It is well known to drive prefabricated sheet piles into the ground in interlocking fashion to provide a retaining wall behind which loose fill such as soil or sand is disposed. In order to stabilise and reinforce this fill and to prevent erosion and excessive outward load on the piles it is also known to install horizontal spaced apart grids or mesh which extend back into the fill. This diffuses the outward forces that would otherwise act against the back of the piles by causing the fill to “stack vertically” as opposed to stacking at its natural shallower angle of repose. The outward force imposed against the piles is thus substantially reduced. Such grids or meshes are commonly referred to in the industry as “Geogrids”. In addition it has been determined that further benefits to the wall structure can be obtained by connecting the Geogrids directly to the back sides of the piles whereby said piles are “tied back” into the fill.